Instruction Manual
Sound Level Meter Types 2245 –
Instruction Manual
Page 34 of 110
2.14.3 Spectrum Measurements
The definition of the measured quantities is the same as for the broadband
measurements.
At low frequency bands the exponential time constants for Fast and Slow weighting are
modified to get a reasonable B*T product, see section 4.11.5.
2.14.4 Instantaneous Spectrum Measurements
The Instantaneous Spectrum Measurements can measure instantaneous time-weighted
sound level
L
xy
, where:
x
is A for A-weighted, B for B-weighted, C for C-weighted or Z for Z-weighted
y
is F for Fast-weighted or S for Slow-weighted
The symbols used by the sound level meter for instantaneous time-weighted sound
level spectrums are (for A, B, C and Z frequency weighting and F and S time weighting):
L
AF
,
L
AS
,
L
BF
,
L
BS
,
L
CF
,
L
CS
,
L
ZF
,
L
ZS
Overload is common to the broadband measurements.
2.14.5 Timed Spectrum Measurements
The Timed Spectrum Measurements can measure minimum time-weighted sound level,
L
xymin
, maximum time- weighted sound level,
L
xymax
, and equivalent continuous sound
level,
L
xeq
, where:
x
is A for A-weighted, B for B-weighted, C for C-weighted or Z for Z-weighted
y
is F for Fast-weighted or S for Slow-weighted
The symbols used by the sound level meter for minimum time-weighted sound level
spectrum, maximum time-weighted sound level spectrum and equivalent continuous
sound level spectrum are (for A, B, C and Z frequency weighting and F and S time
weighting):
L
AFmin
,
L
ASmin
,
L
BFmin
,
L
BSmin
,
L
CFmin
,
L
CSmin
,
L
ZFmin
,
L
ZSmin
,
L
AFmax
,
L
ASmax
,
L
BFmax
,
L
BSmax
,
L
CFmax
,
L
CSmax
,
L
ZFmax
,
L
ZSmax
,
L
Aeq
,
L
Beq
,
L
Ceq
,
L
Zeq
Latched Overload is common to the broadband measurements.
Timed Spectrum Measurements can be reset in the same way as Timed Broadband
Measurements (section 2.14.2). As stated above, the exponential time constant is
modified at low frequencies. This leads to longer settling times at low frequencies.